Interfacial Hydrogen Bonding Engineering of Porous Photothermal Hygroscopic Composites for Sustainable Atmospheric Water Harvesting

Atmospheric water harvesting (AWH) is a promising approach for sustainable freshwater production, with hygroscopic materials playing a central role. However, existing adsorbents still face the challenge of balancing water absorbability, photothermal-conversion efficiency, and long-term cycling stability. Herein, a synergistic strategy based on multicomponent interfacial hydrogen-bond engineering is proposed. A porous photothermal composite comprising poly(vinyl alcohol) (PVA), sodium alginate (SA), carboxylated carbon nanotubes (CNT-COOH), and super hygroscopic MOF (SHM) (PVA/SA/CNT-COOH@SHM) was successfully fabricated. CNT-COOH enables effective photothermal conversion, while SHM acts as a high-density adsorption-site carrier within the flexible three-dimensional PVA/SA network. PVA/SA/CNT-COOH@SHM exhibits a water adsorption capacity of 636.4 mg g–1 day–1, representing a 215.6% improvement compared with PVA/SA/CNT-COOH. Under 1 sun illumination, 83.6% of the adsorbed water is released within 60 min and the adsorption-capacity retention remains as high as 99.1% after 10 consecutive cycles. Furthermore, the composite demonstrates humidity-responsive color-changing behavior owing to electron structure modulation, suggesting its potential applications in smart responsive devices. This study not only provides a low-cost, high-performance, and sustainable material solution for AWH technology but also offers new insights into the design of multifunctional composites through interfacial engineering strategies.